Dynamic Backrest Construction

Abstract

A resilient backrest dampening mechanism is provided for use with chairs having a seat and a backrest, the mechanism comprising four pivot points; a first pivot point arranged on a base different from the backrest; a second pivot point arranged at a distance from the first pivot point on the base, wherein a bracket is pivotally connected to the second pivot point; a third pivot point provided between the bracket and a first end of a backrest connection member, and the backrest connection member being adjustably connected to the backrest; a fourth pivot point provided in the bracket; a resilient member arranged between the fourth pivot point and the first pivot point, and wherein all the pivot points pivot around corresponding axes and all of the axes are parallel.

Claims

1. A resilient backrest dampening mechanism for use with chairs having a seat and a backrest, said mechanism comprising: a first pivot point arranged on a base different from the backrest; a second pivot point arranged at a distance from the first pivot point on said base; wherein a bracket is pivotally connected to said second pivot point; a third pivot point provided between said bracket and a first end of a backrest connection member, and said backrest connection member is adjustably connected to the backrest; a fourth pivot point provided in said bracket; and wherein between the fourth pivot point and the first pivot point is arranged a resilient member, all said pivot points pivot around a corresponding axis, and wherein all pivot axes are parallel.

2. The resilient backrest dampening mechanism according to claim 1, wherein: the fourth pivot point is provided in a sliding sub-bracket integrated in the bracket where sliding of the sub-bracket is controlled, and where when sliding the sub-bracket a distance between the first and fourth pivot points is changed thereby changing an influence of the resilient member.

3. The resilient backrest dampening mechanism according to claim 1, wherein: the third pivot point comprises an oblong aperture in the bracket, and where the first end of the backrest connection member is provided with an axle constituting the corresponding axis, where said axle is controllably guided in said oblong aperture, such that the distance between the second pivot point and the third pivot point may be adjusted.

4. The resilient backrest dampening mechanism according to claim 3, wherein: a longitudinal direction of the oblong aperture is oriented substantially tangentially to the second pivot point.

5. The resilient backrest dampening mechanism according to claim 1, wherein: the resilient member is at least one of a gas-spring, pneumatic-spring, hydraulic-spring, helical spring, or air-cushion.

6. The resilient backrest dampening mechanism according to claim 5, wherein: the gas spring is a locking gas spring allowing the distance between the first and fourth pivot points or a distance between the first and third pivot points to be locked, the gas spring remaining resilient.

7. The resilient backrest dampening mechanism according to claim 2 wherein: a position of the sub-bracket relative to the bracket is adjusted by a threaded aperture in the sub-bracket and a threaded bolt, said bolt having a head portion accessible outside the sub-bracket and bracket, and said bolt having a distal end rotatably fixed in the bracket, whereby rotation of the bolt causes the sub-bracket to move relative to the bracket, and thereby moving the fourth pivot point relative to the first pivot point.

8. The resilient backrest dampening mechanism according to claim 3 wherein: a position of the corresponding axis of the third pivot point axis relative to the bracket is adjusted by providing a threaded aperture in the bracket and a threaded bolt, said bolt having a head portion accessible outside the bracket, and said bolt having a distal end rotatably engaged with the first end of the backrest connection member, whereby rotation of the bolt causes the axle of the backrest connection member to move inside and limited in said oblong aperture, and thereby moving the third pivot point relative to the first pivot point.

9. The resilient backrest dampening mechanism according to claim 2 wherein: a position of the sub-bracket relative to the bracket is adjusted by providing an electrical actuator arranged between the sub-bracket and the bracket.

10. The resilient backrest dampening mechanism according to claim 3 wherein: a position of the axis of the third pivot point relative to the bracket is adjusted by providing an electrical actuator arranged between the bracket and the axle of the back rest connection member or between the bracket and the backrest connection member.

11. The resilient backrest dampening mechanism according to claim 1 wherein: a connection of the resilient member at one end of the connection member or at both ends of said connection member, to the first or fourth pivot points, is dismountable such that a replacement resilient member may be mounted between said first and fourth pivot points.

12. A dampening mechanism adapted for use with a wheelchair having a chassis including a plurality of wheels, a carrying structure, and a support chair mounted on said carrying structure, said support chair having a seat and a backrest, said backrest being pivotally mounted to said support chair or said carrying structure by two hinges, and wherein a resilient backrest dampening mechanism having four pivot points is provided between said backrest and said carrying structure or seat, said dampening mechanism comprising; a first pivot point arranged on a base different from the backrest; a second pivot point arranged at a distance from the first pivot point on said base; a bracket pivotally connected to said second pivot point; a third pivot point provided between said bracket and a first end of a backrest connection member, said backrest connection member being adjustably connected to the backrest; a fourth pivot point provided in said bracket; a resilient member arranged between the fourth pivot point and the first pivot point; all said pivot points pivoting around a corresponding axis, and all said pivot axes being parallel, and wherein the backrest connection member is engaged by a clamping mechanism provided on the backrest to thereby fix the backrest connection member relative to the backrest.

13. A method of using a resilient backrest dampening mechanism according to claim 1, wherein: the backrest of the seat is adjusted to a desired inclination; means provided in a back of the backrest are activated to fixate connection means connecting the backrest to the resilient member thereby activating the resilient member.

14. The method according to claim 13, wherein: the resilient member includes a gas spring installed between the first pivot point and the fourth pivot point thereby providing an adequate counter-force and dampening in response to impact forces on the backrest.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG. 1 illustrates the concept of the present invention;

[0049] FIG. 2 illustrates an embodiment of the invention ready to be mounted in a wheel chair construction;

[0050] FIGS. 3 and 4 illustrate two cross sections of a further embodiment;

[0051] FIG. 5 illustrates a cross section through a wheel chair construction; and

[0052] FIGS. 6A, 6B, and 7 illustrate a complete seating construction suitable for a wheel chair for special purposes.

DETAILED DESCRIPTION OF THE INVENTION

[0053] In FIG. 1 is illustrated the concept of the present invention. The mechanism 1 is arranged on a base 10. On the base is arranged two fastenings creating a first pivot point 4 and a second pivot point 6. The second pivot point is connected to a bracket 12 such that the bracket may pivot relative to the second pivot point and thereby to the base 10. In the bracket 12 is provided a sub-bracket 14 as well as an aperture 16. In the aperture 16 is provided a third pivot point 18. The third pivot point is connected to back-rest connection means 20 which in a first end is connected to the third pivot point and in an opposite end (not illustrated) is releasably and/or adjustably connected to a back-rest. Turning back to the sub-bracket 14, a fourth pivot point 24 is provided such that a resilient member 22 may be connected between the first pivot point 4 and the fourth pivot point 24.

[0054] The sub-bracket 14 is arranged in the bracket 12 such that it may slide whereby the distance between the fourth pivot point 24 provided in the sub-bracket 14 comes closer or further away from the first pivot point 4.

[0055] All the axes of the four pivot points 4, 6, 24, 18 are parallel and as such the pivoting action is maintained in a single plane orthogonal to the orientation of the pivot axis. In order to control the sliding of the sub-bracket 14 relative to the bracket 12 and thereby the distance between the fourth pivot point 24 and the first pivot point 4, a threaded member in the shape of a bolt 26 is provided in the sub-bracket 14.

[0056] The back-rest connection member 20 is pivotally connected to the bracket through the third pivot 18. In the opposite end of the connection members 20, they are (not illustrated) releasably attached to the back-rest. In this manner it is possible to adjust the back-rest completely and independently of the resilient mechanism as neither the hinges nor the seat nor the back-rest itself are directly connected to the mechanism and as such once the comfort position of the seat and back-rest has been attained, it is possible to lock the back seat to the connection members 20 and thereby engage the resilient back-rest dampening mechanism.

[0057] The resilient back-rest dampening mechanism is also adaptable to the loads or impacts that it will be exposed to. By changing the distance between the fourth pivot point and the first pivot point, the actual distance between the fourth pivot point and a third pivot point will also change and thereby the actual distance which will influence the resilient member. If the force is constant and the arm changes, the resulting force will be changed. By adjusting the distance by rotating the bolt 26 it is possible to create a more or less firm dynamic dampening action with this mechanism.

[0058] In other situations it is desirable to replace the resilient member 22 by another resilient member having different characteristics such that for example for very light loads, the dampening mechanism will also be fulfilling its purpose namely to dampen the impacts applied to the back-rest by having a resilient member 22 which is softer. Also the opposite situation is naturally possible by installing a much firmer resilient member 22.

[0059] The sliding distance of the sub-bracket relative to the bracket determines a span of loads to which the mechanism works and also a range within which it is possible to adjust the dampening mechanism's counterforce when it is exposed to loads.

[0060] In FIG. 2 is illustrated an embodiment of the invention ready to be mounted in a wheel chair construction. The resilient back-rest dampening mechanism 2 is in this embodiment a more or less independent device which by means 30 such as apertures positioned in the base 10 may by fastened to a seating construction for example in a wheel chair. In this view the device 2 has been provided with appropriate covering such that only the first and second pivot points 4, 6 are visible whereas the other pivot points are covered by a cover 32. The back-rest connection member 20 extends outside the cover. At the rear end 32 of the cover 32, an aperture 34 is provided through which the bolt 26 is accessible such that by turning the bolt as indicated by the illustrations 36 on the cover 32, the dynamic force absorption properties may be adjusted up or down indicated by the plus and minus, such that the dampening mechanism is able to dampen the forces applied to the back-rest.

[0061] In FIGS. 3 and 4, two cross sections are illustrated through a further embodiment. From the outside it may be similar to the embodiment illustrated in FIG. 2. In FIG. 3 the first to fourth pivot points 4, 6, 18, 24 may be identified. The access aperture 34 provided in the cover 32 is illustrated as providing access to the bolt 26 such that the sub-bracket 14 may be brought closer to the first pivot point 4.

[0062] In this embodiment, there is no sub-bracket, but instead a longitudinal aperture is provided in the bracket 12. The bracket 12 comprises a lever arm 40 engaging an engagement unit 42 which engagement unit in turn is part of the fourth pivot point. Furthermore, the third pivot point's axle is guided in an oblong aperture 16 provided in the bracket. The first end of the back rest connection member is integral with the axle. A bolt 26 is threadedly engaged in the first end of the back rest connection member and the bracket, such that when the bolt is rotated the first end of the back rest connection member and the axle 18 move in the oblong aperture 16.

[0063] In this manner when the bolt 26 is rotated, the lever arm and the engagement unit are moved along the thread provided on the bolt 26. When rotating the bolt 26, a nut-like threaded section 44 will cause the bolt to be screwed more or less into or out of the nut-like construction 44 thereby displacing the lever arm and returning the engagement unit 40, 42. In this view the third pivot point is hidden by the nut-like member 44.

[0064] Turning to FIG. 4, a cross section of the mechanism 2 in a different plane is illustrated. In this view it is easy to detect the second pivot point 6 providing the bracket 12 with means to pivot around the pivot axis in pivot point 6. Also the axle 18 arranged in the oblong aperture is clearly indicated.

[0065] Turning to FIG. 5 a cross section through a wheel chair construction 100 is illustrated. The same seating construction is illustrated in different views in FIGS. 6A and 6B. Turning back to FIG. 5, it may be seen that the back-rest 110 is coupled to a seat by a hinge (not illustrated) completely different/separate from the present invention. The resilient backrest dampening mechanism 2 appears completely separate from the back-rest 110 and the seat 120. In this embodiment, however, the seating construction 120 provides the base 10 for the resilient back-rest dampening mechanism such that from the base 10, the first pivot point 4 is provided in a flange 4 upstanding from the base 10. Likewise the second pivot point 6 is provided adjacent the base 10 and the further pivot points are arranged as described above with reference to FIGS. 3 and 4.

[0066] The back-rest connection member 20 extends from the resilient back-rest dampening mechanism upwards and is engaged in a mechanism 130, provided on the rear of the back-rest construction. In this embodiment, the back-rest connection member 20 is received in a clamping mechanism where a second bolt means 132 is used to fixate the back-rest connection member's position relative to the resilient back-rest dampening mechanism 2 and the back-rest 110. By altering the position in which the clamping mechanism 130 and thereby the bolt 132 engages the back-rest mechanism, the inclination of the entire back-rest relative to the seat 120 may be adjusted completely independently of the resilient back-rest dampening mechanism 2.

[0067] In FIGS. 6A and 6B is illustrated a complete seating construction 100 suitable for a wheel chair for special purposes. The various aspects not related to the resilient back-rest dampening mechanism will not be mentioned. As is clear from FIG. 6A, the resilient back-rest dampening mechanism is completely integrated in the seating construction such that the rear end 32 of the cover 32 is visible from the rear of the seat and also the aperture 34 through which the bolt 26 (see FIG. 3) is accessible. The back-rest connection members 20 may also be seen. Turning to FIG. 6B, the same seat 100 is seen from the front and in this view only the cover 32 of the resilient back-rest dampening mechanism is visible. Particularly from FIGS. 6A and 6B it is clear that the back-rest and the seat are connected by hinge means 140 which are completely separate from the resilient back-rest dampening mechanism.

[0068] A similar view is illustrated in FIG. 7.

[0069] Above the invention has been described with reference to a specific embodiment but it is clear that the skilled person will recognize that other adaptations and implementations are also contemplated within the scope of the appended claims.